Microstructure and transport properties of sol–gel derived highly (100)-oriented lanthanum nickel oxide thin films on SiO2/Si substrate

In the present work, lanthanum nickel oxide (LNO) thin films were prepared by the sol–gel method and different thermal treatments were adopted by adjusting the preheating treatment. The microstructure, crystal orientation, chemical composition and electrical properties of LNO films were analyzed to elucidate the relationship between the microstructure and the transport properties of the films. The results show that equiaxed grains predominate the microstructure of the films with pyrolysis step. Without the pyrolysis step, columnar grains are formed in the films, accompanied with an improvement in crystallinity and strengthening of the (100)-orientation. Furthermore, the metal–insulator transition temperature decreases for the films without the pyrolysis step. The effect of film microstructure on its electrical properties was discussed in terms of the existence of internal stress and the improved crystallinity.

► Preparation of highly (100)-oriented LNO films on amorphous SiO2/Si substrate.
► Formation of columnar grains in the films by adjusting heating process.
► Decrease of metal–insulator transition temperature for films with improved structure.